Torque Vectoring Device With Planetary Gear Set For Connection To Balancing Shaft

ABSTRACT

A device for torque vectoring in a wheeled vehicle is presented. The device includes a differential mechanism arranged on an axle having a first drive shaft and a second drive shaft, an electrical power source connected to an electrical motor, the electrical motor being connectable to the axle for torque vectoring between the first drive shaft and the second drive shaft, and control means connected to the power source and configured to receive a plurality of variables representing the current vehicle state and to determine drive currents being dependent on the variables, wherein the drive currents are supplied to the electrical motor from the power source for introducing a torque increase to either one of the first or second drive shafts and a corresponding torque decrease to the other one of the first or second drive shafts.

FIELD OF THE INVENTION

The present invention relates to a device for torque vectoring. Moreparticularly, the present invention relates to a device for applying atorque difference between first and second drive shafts of an axle of awheeled vehicle.

BACKGROUND OF THE INVENTION

In a road vehicle, especially a car, it is advantageous to be able tofreely distribute drive torque to different wheels in order to enhancethe driving dynamics of the vehicle. Devices for accomplishing thisdesired result are in the art referred to as torque vectoring devices.

Torque vectoring devices may be used in either two-wheel drive vehiclesor four-wheel drive vehicles, although the latter case must presently beregarded as more common. It can also be used for either rear or frontdrive shafts or in the cardan shaft for distributing torque between thefront and rear drive shafts.

In order to obtain the desired result with regard to the drivingdynamics, it may in certain situations be advantageous to provide adrive wheel with a positive torque in relation to the other drive wheelon the driving axle. Such a positive torque may be obtained in a wayknown per se by a mechanical gear device for gearing-up or increasingthe rotational speed of the drive shaft for the wheel in question by forexample 10%.

Many examples of such mechanical gear devices are known. In sucharrangements being both heavy and expensive, torque vectoring devicesare arranged at either side of the central differential for the twodrive shafts.

Hence, when a differential rotational speed between two wheels isrequested the prior art devices are affecting the rotational speedrelative the absolute rotational speed, leading to heavy devices havinga relatively high power consumption.

SUMMARY OF THE INVENTION

Accordingly, the present invention preferably seeks to mitigate,alleviate or eliminate one or more of the above-identified deficienciesin the art and disadvantages singly or in any combination and solves atleast the above-mentioned problems by providing a device according tothe appended patent claims.

It is an object of the invention to provide a torque vectoring device,which overcomes the above mentioned problems.

A further object of the present invention is to provide an efficienttorque vectoring device being configured to be implemented in a modernvehicle.

Moreover, an object of the present invention is to provide a torquevectoring device which has a significantly reduced size and energyconsumption.

According to an aspect, a device for torque vectoring in a wheeledvehicle is provided. The device comprises a differential mechanismarranged on an axle having a first drive shaft and a second drive shaft,an electrical power source connected to an electrical motor, saidelectrical motor being connectable to said axle for torque vectoringbetween said first drive shaft and said second drive shaft, and controlmeans connected to said power source and configured to receive aplurality of variables representing the current vehicle state and todetermine drive currents being dependent on said variables. Said drivecurrents are supplied to said electrical motor from said power sourcefor introducing a torque increase to either one of said first or seconddrive shafts and a corresponding torque decrease to the other one ofsaid first or second drive shafts. This is advantageous in that thedevice may be made relatively small, as it requires the electrical motorto only operate at a rotational speed being proportional to thedifferential rotational speed, instead of at a rotational speed beingproportional to the absolute rotational speed.

Said electrical power source may comprise an accumulator, and saidcontrol means may comprise a vehicle communication network configured tocollect the plurality of variables, a controller configured to receivesaid variables and calculate one or more control signals, and a powerelectronics unit configured to receive said one or more control signalsand to control the energy flow between the accumulator and theelectrical motor by supplying said drive currents via the accumulator.Hence, the device may be used for real time state detection such thatthe device may be used as a tractive enhancement feature on surfaceshaving inhomogeneous friction.

The device may further comprise an electrical propulsion motor arrangedto drive said axle. This is advantageous in that a common electricalsystem may be used for the electrical motor and the propulsion motor,thus reducing size and complexity of the device.

The electrical propulsion motor may be arranged at said axle such that arotor of said electrical propulsion motor is rotating around the axis ofsaid axle. Hence, no components are necessary for transmitting torque tothe axle leading to a more compact device.

The differential mechanism may comprise a differential, which isadvantageous in that readily available components may be used, and theelectrical motor may be connected to the first drive shaft and saidsecond drive shaft by means of a planetary gear set, wherein theelectrical motor is driving a sun gear, the first drive shaft isconnected to a ring gear, and wherein the second drive shaft isconnected to planetary gears. In such embodiment, the gear ratios of theplanetary gear set may be designed such that no torque is transmittedthrough the planetary gear set when the electrical motor is deactivated.Further, the gear ratios of the planetary gear set may be designed suchthat the electrical motor is standing still when the first drive shaftand the second drive shaft are rotating at the same rotational speed.This means that possible loss of energy is reduced.

The differential mechanism may comprise a first planetary gear setconnected to the first drive shaft, and a second planetary gear setconnected to the second drive shaft, and said electrical motor may beconnected to said first drive shaft and said second drive shaft by meansof two gears rotating at different directions, wherein said gears areconnected to each other by means of a shaft extending along the axle.Hence, the shaft connecting the gears is designed to stand still whenthe first drive shaft and the second drive shaft are rotating at thesame rotational speed. Further, the shaft is designed to rotate at aspeed being proportional to the differential rotational speed betweenthe first drive shaft and the second drive shaft. Since the differentialrotational speed at most times will be zero, or very close to zero,energy losses will be reduced.

The electrical motor may be connected to a clutch configured to decouplethe rotational axis of the electrical motor from said differentialmechanism. The clutch may be automatically decoupled when the rotationalspeed of said clutch is exceeding a predetermined threshold value.Alternately or additionally, the control means may be configured tocause automatic decoupling of said clutch based on an analysis of atleast one of said plurality of variables representing the currentvehicle state. This is advantageous in that the electrical motor isprotected against overload, e.g. in transient vehicle conditions such asESP intervention.

Said propulsion motor may be connected to a mechanical disconnect unitconfigured to disconnect the propulsion motor from said axle.Alternately or additionally, said control means may be configured tocause automatic actuation of said mechanical disconnect unit based on ananalysis of at least one of said plurality of variables representing thecurrent vehicle state, so as to disconnect the propulsion motor fromsaid axle. This is further advantageous in that high losses, occurringfrom drag torque and field weakening during high speed, may be reducedor eliminated.

Said power electronics unit may be further configured to control theenergy flow between the accumulator and the propulsion motor bysupplying drive currents to said propulsion motor via the accumulator,and the power electronics unit may be further configured to allowreverse energy flow for charging the accumulator during braking of thevehicle. Regenerative braking may thus be used to decrease the energyconsumption of the vehicle.

Said controller may be configured to execute a plurality of controlprograms, each control program being designed to control a respectiveaspect of the driving dynamics of the vehicle by appropriatelycalculating torque requests to said electrical motor, as represented bysaid one or more control signals to the power electronics unit, based onsaid plurality of variables representing the current vehicle state.

Said controller may further comprise arbitration functionalityconfigured to handle concurrent torque requests from different ones ofsaid control programs by prioritizing among such concurrent requests andpermitting, combining or inhibiting each individual concurrent torquerequest as deemed most appropriate.

BRIEF DESCRIPTION OF THE DRAWINGS

Hereinafter, the invention will be described with reference to theappended drawings, wherein:

FIG. 1 is a schematic view of a vehicle according to an embodiment;

FIG. 2 is a schematic view of a vehicle according to another embodiment;

FIG. 3 is a schematic view of a vehicle according to a furtherembodiment;

FIG. 4 is a schematic view of a vehicle according to a yet furtherembodiment;

FIG. 5 is a schematic view of a vehicle according to another embodiment;

FIG. 6 is a schematic view of a torque vectoring device according to anembodiment;

FIG. 7 is a cross sectional view of a torque vectoring device accordingto an embodiment;

FIG. 8 is a cross sectional view of a torque vectoring device accordingto a further embodiment;

FIG. 9 is a cross sectional view of a clutch for use within a torquevectoring device according to an embodiment; and

FIG. 10 is a block diagram illustrating, on a schematic level, how atorque vectoring device of FIGS. 7-8 can be controlled by a controllerdevice in order to regulate the dynamics of a vehicle.

DETAILED DESCRIPTION OF THE INVENTION

Several embodiments of the present invention will be described in moredetail below with reference to the accompanying drawings in order forthose skilled in the art to be able to carry out the invention. Theinvention may, however, be embodied in many different forms and shouldnot be construed as limited to the embodiments set forth herein. Rather,these embodiments are provided so that this disclosure will be thoroughand complete, and will fully convey the scope of the invention to thoseskilled in the art. The embodiments do not limit the invention, but theinvention is only limited by the appended patent claims. Furthermore,the terminology used in the detailed description of the particularembodiments illustrated in the accompanying drawings is not intended tobe limiting of the invention.

Examples of drive line configurations of a vehicle are shown in FIGS. 1to 6. In these embodiments, the vehicle 10 has a front axle 12 beingconnected to a rear axle 14, and a torque vectoring device 16. In FIG.1, the front axle 12 is driven by means of a transmission 18, and therear axle 14 is driven by means of an electrical motor 20. The torquevectoring device 16 is arranged at the rear axle 14. In FIG. 2, asimilar configuration is shown but here the rear axle is driven by meansof a transmission 18, and the front axle is driven by means of anelectrical motor 20. Consequently, the torque vectoring device 16 isarranged at the front axle. FIGS. 3 and 4 show configurations where thefront axle 12 or the rear axle 14 is driven by an electrical motor 20,wherein the torque vectoring device 16 is arranged at the driven axle12, 14. As a further example, FIG. 5 shows a configuration in which thefront axle 12 and the rear axle 14 are driven by electrical motors 20.

With reference to FIG. 6, a basic setup of a torque vectoring device 100is shown. A driving axle 110 of a vehicle is driven by means of atransmission 120 and has two wheels 112 a, 112 b connected to oppositeends of the axle 110. The transmission 120 is coupled to a differentialmechanism 130 for allowing the wheels 112 a, 112 b to rotate atdifferent velocities. An electrical motor 140 is connected to thedifferential mechanism 130, for providing a torque difference toopposite ends of the axle 110. A control means 150 is further connectedto the electrical motor 140, and configured to calculate and transmitcontrol signals to the electrical motor 140.

When the vehicle is travelling on a straight course, both wheels 112 a,112 b will rotate at the same speed. In this situation, the electricalmotor 140 will stand still. When the vehicle passes a surface havinginhomogeneous friction, the torque vectoring device 100 may be used toenhance the traction potential of the driving axle 110. In such cases,the control means 150 sends a signal to the electrical motor 140 thatwill activate and apply a torque. Upon this, an increase of torque willbe provided to one of the ends of the axle 110, and a correspondingtorque decrease will be provided to the opposite end of the axle 110.

An embodiment of a torque vectoring device is shown in FIG. 7. Anelectrical propulsion motor 200 transmits torque from a rotating shaft202 to a driving axle 210 via gears 204, 205, 206, 207, 208. The drivingaxle 210 has a central portion 212, and first and second drive shafts214, 216. The central portion 212 is connected to the first and seconddrive shafts 214, 216 by means of two planetary gears 220 a, 220 b. Thecentral portion 212 is connected to sun gears 222, and the first driveshaft 214 and the second drive shaft 216 are connected to a plurality ofplanet gears 224. A ring gear 226 is provided with teeth on its outersurface, for engagement with a torque vectoring motor 230. The torquevectoring motor 230 is an electrical motor, which upon activationtransmits a rotation to a rotating shaft 240 via an axis 232 and gears234, 236. The rotating shaft 240 extends along the axis of the axle 210,and has a first gear 242 that is engaged with the ring gear 226 of thefirst planetary gear 220 a, and a second gear 244 that is engaged withthe ring gear of the second planetary gear 220 b via an intermediategear 246. When the torque vectoring motor 230 is activated, the motor230 will provide a torque. Consequently, if the torque vectoring motor230 is rotating, which will be determined by the actual state of thevehicle, opposite rotation of the ring gears 226 will be induced. Hence,an increase of torque is provided to one of the drive shafts 214, 216,and a decrease of torque is provided to the other of said drive shafts214, 216 via the planetary gears 220 a, 220 b.

Optionally, the electrical propulsion motor 200 may be arranged on thecentral portion 212 of the driving axle 210. However, if the propulsionmotor 200 is arranged at a distance from the axle 210 a number ofadvantages are obtained. For example, such arrangement will facilitateimplementation of a mechanical disconnect functionality of thepropulsion motor 200 which will be described in more detail later.Moreover, the planetary gears 220 a, 220 b can be made smaller as theydo not need to correspond to the dimensions of the propulsion motor 200.A further advantage is that the cooling of the axle 210 is simplified,since access is readily allowed if the propulsion motor 200 is locatedat a distance from the axle 210.

Another embodiment of a torque vectoring device is shown in FIG. 8. Anelectrical motor (not shown) transmits torque to a driving axle 310 viaa differential unit 320. The torque is equally distributed between afirst and a second drive shaft 314, 316 by the differential unit 320.The first drive shaft 314 is provided with a gear 318 having outer teethand being arranged to rotate about the same central axis as the firstdrive shaft 314. The second drive shaft 316 is provided with a gear 319having outer teeth and being arranged to rotate about the same centralaxis as the second drive shaft 316.

A torque vectoring motor 330 is provided to transfer torque from thefirst drive shaft 314 to the second drive shaft 316, or vice versa. Thetorque vectoring motor 330 is connected to the sun gear 342 of aplanetary gear 340. The ring gear 346 is connected to the first driveshaft 314 by the gears 318, 348. Further, a planetary carrier 344 isconnected to the second drive shaft 316 by means of a shaft 350 andgears 319, 349.

When the torque vectoring motor 330 is activated, the motor 330 willprovide opposite torque to the gears 318, 319. Hence, an increase oftorque is provided to one of the drive shafts 314, 316, and a decreaseof torque is provided to the other of said drive shafts 314, 316 via theplanetary gear set 340.

If the gear ratios of the gears 318, 348, and 319, 349, respectively,are matched to the gear ratio of the planetary gear set 340, the torquevectoring motor 330 will be standing still when the first and seconddrive shafts 314, 316 have equal rotational speed. If so, the followingcondition must be fulfilled:

${\frac{i_{1}}{i_{2}} = {2 \cdot \frac{r_{01} + r_{02}}{r_{01} + {2 \cdot r_{02}}}}},$

where

i₁ is the gear ratio between the gears 318, 348, i₂ is the gear ratiobetween the gears 319, 349, r₀₁ and r₀₂ are the reference radii of theplanetary gear set 340. The above parameters may be chosen to achievereasonable speed and torque requirements on the torque vectoring motor.For example, in a particular configuration i₁ is set to 3, i₂ is 2.67,r₀₁ is 8, and r₀₂ is 28.

In any of the embodiments mentioned, the torque vectoring motor 230, 330may be a variable speed reversible electrical motor.

As is shown in FIGS. 7 and 8, the torque vectoring motor 230, 330 may beconnected to a device 260, 360 providing mechanical protection againstoverload in transient vehicle conditions, such as ESP intervention. Anautomatic clutch 260, 360 is thus provided to disconnect the torquevectoring motor 230, 330 when the rotational speed exceeds apredetermined de-clutch limit. An example of such automatic clutch 260,360 is presented in FIG. 9. The automatic clutch 260, 360 has a clutchdrum 265 connected to the shaft 240, 350 and at least two lever arms 263being connected to the drum 265 by pivot joints 262. A hub 261 isconnected to the motor 230, 330 such that rotational speeds below thede-clutch limit are transferred from the hub 261 to the drum 265 via thefriction between the lever arms 263 and the hub 261. When the rotationalspeed reaches the de-clutch limit, the centrifugal force acting on thelever arms 263 will exceed a spring force, and no torque can thus betransferred. Hence, the centrifugal clutch 260, 360 will disconnect thetorque vectoring motor 230, 330 at a certain rotational speed to protectit from over speeding. In another example, the control means 150, 420,430, 440 is configured to cause automatic decoupling of the clutch 260,360 based on an analysis of at least one of the plurality of variables442, 444 representing the current vehicle state. For example, automaticdecoupling of the clutch 260, 360 may be based on an analysis of therotational speed of the electrical motor 230, 330, wherein therotational speed is measured by at least one sensor providing themeasured value as one of the variables 442, 444.

In a yet further embodiment, a mechanical disconnect unit of apropulsion motor 200 is provided. Such disconnect unit can be adapted todisconnect the propulsion motor at a certain speed by either acentrifugal disconnect unit similar to the clutch described withreference to FIG. 9, or e.g. by a dog clutch or a limited slip clutchbeing controlled by a microprocessor. Depending on the specific type ofthe propulsion motor, there may be high losses at high speeds comingfrom drag torque and field weakening. By disconnecting the propulsionmotor, such losses can be minimized and hence the fuel saving potentialmay be maximized. When the propulsion motor is disconnected, the torquevectoring motor may still be used and thus always be utilized toinfluence vehicle stability. In a specific embodiment, the control means150, 420, 430, 440 is configured to cause automatic actuation of themechanical disconnect unit based on an analysis of at least one of saidplurality of variables 442, 444 representing the current vehicle state,so as to disconnect the propulsion motor 20, 200, 400 from the axle 110,210, 310, 402.

A speed gear may be arranged between the propulsion motor 200 and thedriving axle 110, 210, 310. The speed gear, such as a transmission knownper se, is thus used for converting the speed and torque of thepropulsion motor. This is advantageous in that the electrical propulsionmotor 200 is allowed to operate at its optimum speed interval, thusreducing the overall energy consumption of the vehicle.

For all embodiments described so far, it is assumed that the torquevectoring motor 230, 330 receives control signals from a control meansarranged within the vehicle. The control means is configured to receivea plurality of vehicle variables and to determine a corresponding outputsignal that is transmitted to the torque vectoring motor. For example,the control means comprises a vehicle network communication interfaceconfigured to collect the plurality of vehicle variables, a controllerconfigured to receive said vehicle variables and calculate the outputsignal, and a power electronics unit configured supply drive currents tothe electrical motor in response to the output signal for controllingthe energy flow between an electrical power source and the electricalmotor. The electrical power source may for example be an electricalaccumulator like a battery or fuel cell, or an electrical generator. Inone particular embodiment, in which the torque vectoring device 100,200, 300 is implemented in a vehicle being at least partly driven by acombustion engine, the electrical power source may be a generator drivenby said combustion engine. In a further embodiment, the generator may bedriven by a separate combustion engine. However, in the embodimentdescribed in the following paragraphs, the electrical power source is anelectrical accumulator.

A description of how a torque vectoring device according to any of theembodiments referred to above may be applied in a modern road vehicle,such as a car (automobile), will now follow with reference to FIG. 10.As seen in FIG. 10, a car 400 comprises a first axle 402 which is drivenby a first axle drive mechanism 404. As is well known per se, adifferential mechanism 406 on the first axle 402 allows a left driveshaft 402 _(L) of the first axle 402, and a left wheel 408 _(L) mountedthereon, to rotate at a different speed than a right drive shaft 402 ₈of the first axle 402, and a right wheel 408 ₈ mounted thereon. A torquevectoring motor 410—which for instance may be implemented by theelectrical motor 140, 230 or 330 referred to above—is arranged toprovide a torque increase 411 _(I) on one of the drive shafts 402, 402 ₈and a corresponding torque decrease 411 _(D) on the other one of thedrive shafts 402 ₈, 402 _(L), as has already been explained withreference to the previous drawings. In FIG. 10, the torque increase 411_(I) is applied to the left drive shaft 402 _(L), whereas the torquedecrease 411 _(D) is applied to the right drive shaft 402 ₈. However, byreversing the rotation of the torque vectoring motor 410, the situationwill be the opposite.

The torque vectoring motor 410 is driven by drive currents 412 which aresupplied from an electrical power source in the form of an accumulator424 via a power electronics unit 420. In turn, the power electronicsunit 420 is controlled by means of one or more control signals 422 froma torque vectoring controller 430. The amplitude and polarity of thedrive currents 412 will determine the rotational speed and direction ofthe torque vectoring motor 410 and, consequently, the magnitude anddirection of the torque increase/decrease 411 _(I)/411 _(D) applied tothe left and right drive shafts 402 _(L), 402 _(R).

Like any electrical machine, the torque vectoring motor 410 may not onlyact as a motor but may also be driven as a generator to transformmechanical energy from the rotation of the first axle 402 intoelectrical energy to be received and stored in the accumulator 424. Thismay advantageously be used for regenerative braking in order to reducethe electrical energy consumption of the vehicle and to extend therecharging periodicity of the accumulator 424. To this end, the powerelectronics unit 420 is adapted to closely control the flow ofelectrical energy from the accumulator 424 to the torque vectoring motor410 (when operating as a motor), and to the accumulator 424 from thetorque vectoring motor 410 (when operating as a generator),respectively. The power electronics unit 420 therefore compriseshigh-efficiency solid-state circuitry capable of accurate control of thedrive currents 412 to the torque vectoring motor 410 (motor case), andof the generated currents fed to the accumulator 424 (generator case).Accurate control is particularly important in the latter case, since thecapacity, life-time and safety of the accumulator 424 (for instance inthe form of one or more state-of-the-art, high-energy lithium batteries)may otherwise be jeopardized.

In embodiments of the vehicle 400, the first axle drive mechanism 404,too, may comprise an electrical motor. In such a case, also thiselectrical motor 404 may be driven by drive currents 414 from the powerelectronics unit 420, and, conversely, also the electrical motor 404 maybe used as a generator for charging the accumulator 424 under thecontrol of the power electronics unit 420.

As already mentioned, the power electronics unit 420 is in turncontrolled by means of one or more control signals 422 from the torquevectoring controller 430. The torque vectoring controller 430, which maybe identical to the aforementioned control means 150, is preferablyimplemented as a microprocessor (PLC, CPU, DSP) or another suitableprocessing device technology, such as FPGA or ASIC, or any othersuitable digital and/or analogue circuitry capable of performing theintended tasks. In order to be able to exercise the control of thetorque vectoring motor 410 and generate the control signals 422, thetorque vectoring controller 430 is programmed or otherwise provided withelectrical motor control functionality 432.

The electrical motor control functionality 432 of the torque vectoringcontroller 430 is capable of real-time calculation of various controlvariables, which in turn determine the control signals 422, based on thecurrent vehicle state. To this end, vehicle state data in the form of aplurality of external vehicle variables 442 is collected by a pluralityof sensors distributed across the vehicle. The external vehiclevariables 442 are continuously broadcasted on a vehicle communicationnetwork 440 and are therefore made accessible to the electrical motorcontrol functionality 432 via this network. The vehicle communicationnetwork 440 may for instance be compliant with an industry standardprotocol such as CAN (“Controller Area Network”) and/or FlexRay.

In addition, vehicle state data in the form of vehicle state variables444 may also be also received by the electrical motor controlfunctionality 432 over the network 440. Such vehicle state variables 444may be produced by other units in the vehicle, such as by a mainelectronic control unit (ECU) 450, an anti-lock braking system (ABS) 452or an electronic stability program (ESP) 454. The ECU 450, ABS 452 andESP 454 may be provided for the purpose of controlling a second driveaxle 462 having its own axle drive mechanism 464 (such as a combustionengine, for instance), differential mechanism 466 and pair of wheels 468_(L), 468 _(R). By receiving and using such vehicle state variables 444from other units in the vehicle, the electrical motor controlfunctionality 432 may make sure that the torque vectoring motor 410 (andfirst axle drive mechanism 404, when being an electrical motor) isoptimally driven in view of energy consumption, service life, vehiclestability, traction performance, and driving safety.

Conversely, using the vehicle communication network 440, the torquevectoring controller 430 may be adapted to inform or instruct otherunits in the vehicle concerning control decisions it has made for thetorque vectoring motor 410 (and the first axle drive mechanism 404, whenbeing an electrical motor). For instance, the control of the second axledrive mechanism 464 in the form of a combustion engine may benefit fromtaking such information or instructions into account, since it mayreduce the fuel consumption. Further, the ESP functionality 454 may beimproved and made more accurate by this kind of data from the torquevectoring controller 430.

Thus, by controlling a torque vectoring system together with othersystems, for example ESP 454, synergic effects can be reached. A torquevectoring system can be controlled at lower differential speeds,smoother and more accurately than an ESP can control by using the engineand brake system. Therefore control signal(s) can be broadcasted to theESP 454, informing about actions performed by the torque vectoringsystem or requesting a performance from the ESP system.

For optimal fuel consumption in a hybrid vehicle the engine and theelectrical driven axle should be controlled in a manner to reach minimumfuel consumption. This can be done by having an optimization controllerin the electronic module in the electrical axle broadcasting signalsrequesting action from the engine or sending a request from the enginecontroller to the electrical axle.

Examples of control variables provided to and/or calculated by theelectrical motor control functionality 432 from the received vehiclestate data 442, 444 may include driver's acceleration or decelerationrequest (i.e. acceleration or brake pedal position), wheel speeds,steering wheel angle, yaw rate, lateral acceleration, estimated vehiclespeed, actual tire slip values, road friction utilization, level ofover/under steer, and engine/motor torque and speed (for axle drivemechanism 404 or 464). The electrical motor control functionality 432may preferably be divided into a plurality of control programs 433 _(a). . . 433 _(e). Each control program is designed to control a respectiveaspect of the driving dynamics of the vehicle by appropriatelycalculating torque requests to the torque vectoring motor 410, asrepresented by the control signals 422 to the power electronics unit420, so that the torque vectoring motor 410 will be actuated accordinglyto obtain the desired change in torque distribution between the left andright drive shafts 402 _(L), 402 _(R). As seen in FIG. 10, non-limitingexamples of control programs included in the electrical motor controlfunctionality 432 are: Vehicle stability 433 _(a), Traction performance433 _(b), Regenerative braking 433, Hybrid control 433 _(d), and Yawdamping 433 _(e). In the disclosed embodiment, all or at least some ofthese control programs 433 _(a) . . . 433 _(e) are executed in parallelto each other. In other words, the torque vectoring controller 430 iscapable of running the control programs 433 _(a) . . . 433 _(e) in amulti-tasking manner. Having a plurality of concurrently running controlprograms 433 _(a) . . . 433 _(e) provides a broad, flexible andextensive control of the driving dynamics of the vehicle, which truly isof a complex nature.

In addition to the electrical motor control functionality 432, thetorque vectoring controller 430 is programmed or otherwise provided witharbitration functionality 434 and safety/diagnostics functionality 436.

The purpose of the arbitration functionality 434 is to handle situationswhere torque requests are made concurrently from different ones of thecontrol programs 433 _(a) . . . 433 _(e). Since each control programdetermines its torque requests in consideration of the particular needsthat the program in question is tasked to handle, there will besituations where two or more concurrent torque requests are not mutuallycompatible and cannot all be granted. The arbitration functionality 434is designed to prioritize among such concurrent requests and to permit,combine or inhibit each individual request as deemed most appropriate.Hence, the arbitration functionality 434 will prevent potentiallydangerous situations from occurring when concurrent torque requests arein conflict with each other, without unduly restricting the operabilityof each individual control program. The arbitration functionality 434may alternatively or additionally be designed to receive and act uponarbitration instructions from another unit in the vehicle (such as mainECU 450), instead of making the arbitration decisions itself.Furthermore, when the first axle drive mechanism 404 comprises anelectrical motor driven by drive currents 414 from the power electronicsunit 420, the arbitration functionality 434 may advantageously beadapted to handle arbitration also for requests directed to theelectrical motor 404.

The purpose of the safety/diagnostics functionality 436 is to handleerrors among incoming vehicle state data 442, 444, for instanceplausibility checks and offset compensations. Moreover, thesafety/diagnostics functionality 436 supervises the status and operationof the torque vectoring motor 410, power electronic unit 420,accumulator 424 as well as the torque vectoring controller 430 itself,and is designed to broadcast diagnostic information to other units inthe vehicle (for instance main ECU 450).

The invention may be implemented in any suitable form includinghardware, software, firmware or any combination of these. However,preferably, the invention is implemented as computer software running onone or more data processors and/or digital signal processors. Theelements and components of an embodiment of the invention may bephysically, functionally and logically implemented in any suitable way.Indeed, the functionality may be implemented in a single unit, in aplurality of units or as part of other functional units. As such, theinvention may be implemented in a single unit, or may be physically andfunctionally distributed between different units and processors.

It will be appreciated that the embodiments described in the foregoingmay be combined without departing from the scope as defined by theappended patent claims.

Although the present invention has been described above with referenceto specific embodiments, it is not intended to be limited to thespecific form set forth herein. Rather, the invention is limited only bythe accompanying claims and, other embodiments than the specific aboveare equally possible within the scope of these appended claims.

In the claims, the term “comprises/comprising” does not exclude thepresence of other elements or steps. Furthermore, although individuallylisted, a plurality of means, elements or method steps may beimplemented by e.g. a single unit or processor. Additionally, althoughindividual features may be included in different claims, these maypossibly advantageously be combined, and the inclusion in differentclaims does not imply that a combination of features is not feasibleand/or advantageous. In addition, singular references do not exclude aplurality. The terms “a”, “an”, “first”, “second” etc do not preclude aplurality. Reference signs in the claims are provided merely as aclarifying example and shall not be construed as limiting the scope ofthe claims in any way.

According to a further inventive concept in the technical field oftorque vectoring, a device is hereby presented. The device comprises adifferential mechanism arranged on an axle having a first drive shaftand a second drive shaft, a torque generating unit being connectable tosaid axle for torque vectoring between said first drive shaft and saidsecond drive shaft, and a control means connected to said torquegenerating unit for determining the amount of torque that should beapplied for reducing the differential rotational speed between the firstdrive shaft and the second drive shaft. In a preferred embodiment ofthis further inventive concept, the torque generating unit is a brakingunit such as a friction brake, a viscous coupling unit, a dog clutch, ora disc clutch. In a particular embodiment, the torque generating unit isconnected to a control means configured to receive a plurality ofvariables representing the current vehicle state and to determine anoutput signal being dependent on said variables, wherein said outputsignal is supplied to said torque generating unit for reducing thedifferential rotational speed between the first drive shaft and thesecond drive shaft.

With reference to FIGS. 7 and 8, the following modifications arepossible for providing a torque vectoring device according to thefurther inventive concept presented above. The torque generating unit,i.e. the brake or the clutch, may be arranged on the shaft 232 (FIG. 7)or 342 (FIG. 8) instead of or in line with the electrical motor 230,330. As the torque generating unit is also connected to a stationaryportion, the rotational speed of the shaft 232, 342 may be reduced. Ifthe electrical motor 230, 330 is replaced, the clutch 260, 360 may alsobe removed since there is no longer a need for limiting the rotationalspeed.

A viscous coupling unit may provide a braking torque that is dependenton the rotational speed of the shaft 232, 242. A dog clutch may providea binary disconnect or connect coupling, i.e. the shaft 232, 242 iseither free to rotate or locked. A friction brake or a disc clutch mayprovide continuous control of the torque.

For all such torque generating units, the rotational speed of the shaft232, 242 may only be reduced or eliminated. Consequently, thedifferential rotational speed between the wheels of the vehicle may onlybe reduced or eliminated. This is contrary to the functionality when anelectrical motor is implemented, which allows for increase ofdifferential rotational speed between a first drive shaft and a seconddrive shaft.

However, a torque generating unit such as a brake or a clutch may beimplemented together with a torque vectoring motor. In such embodiment,the device may provide a braking torque being higher than the capabilityof the electrical motor alone.

What is claimed is:
 1. A device for torque vectoring in a wheeledvehicle, comprising: a differential mechanism comprising a differentialarranged on an axle having a first drive shaft and a second drive shaft,an electrical power source connected to an electrical motor, saidelectrical motor being connectable to said axle for torque vectoringbetween said first drive shaft and said second drive shaft, wherein saidelectrical motor is connected to said first drive shaft and said seconddrive shaft by means of a planetary gear set, and control meansconnected to said power source and configured to receive a plurality ofvariables representing the current vehicle state and to determine drivecurrents being dependent on said variables, wherein said drive currentsare supplied to said electrical motor from said power source forintroducing a torque increase to either one of said first or seconddrive shafts and a corresponding torque decrease to the other one ofsaid first or second drive shafts.
 2. The device according to claim 1,wherein said electrical power source comprises an accumulator, andwherein said control means comprises: a vehicle communication networkconfigured to collect the plurality of variables, a controllerconfigured to receive said variables and calculate one or more controlsignals, and a power electronics unit configured to receive said one ormore control signals and to control the energy flow between theaccumulator and the electrical motor by supplying said drive currentsvia the accumulator.
 3. The device according to claim 1, wherein theelectrical motor drives a sun gear, the first drive shaft is connectedto a ring gear, and the second drive shaft is connected to planetarygears.
 4. The device according to claim 1, wherein the electrical motoris connected to a clutch configured to decouple a rotational axis of theelectrical motor from said differential mechanism.
 5. The deviceaccording to claim 4, wherein the clutch is automatically decoupled whena rotational speed of said clutch exceeds a predetermined thresholdvalue.
 6. The device according to claim 4, wherein said control means isconfigured to cause automatic decoupling of said clutch based on ananalysis of at least one of said plurality of variables representing thecurrent vehicle state.
 7. The device according to claim 2, wherein saidcontroller is configured to execute a plurality of control programs,each control program being designed to control a respective aspect ofdriving dynamics of the vehicle by appropriately calculating torquerequests to said electrical motor, as represented by said one or morecontrol signals to the power electronics unit, based on said pluralityof variables representing the current vehicle state.
 8. The deviceaccording to claim 7, wherein said controller further comprises anarbitration functionality configured to handle concurrent torquerequests from different ones of said control programs by prioritizingamong said concurrent requests and permitting, combining or inhibitingeach individual concurrent torque request as deemed most appropriate.